That is one of the problems I have with such books. You see, the Tomato Hornworm is NOT the same as the Corn Earworm. And the common Fruitworm will infest several different types of veggies in the garden, not just corn or tomatoes.

Corn worms are corn worms and tomato worms are tomato worms. You may never see either or they may infest each other no matter how close or how far apart you plant the two vegetables because their parents have wings and fly all over the garden to lay eggs.

The school of companion planting isn't all it is cracked up to be and never really caught on because too much of it is misleading and inaccurate information based on assumptions that just don't hold up in actual practice.

The only real concern for most gardeners is if your corn will shade the tomato plants too much or vice-versa. But if you want to experiment with companion planting then I suggest you post your question over on the Companion Planting forum here.

Dave

Here, let's know what we're really discussing:

On a practical note, when the adult moths will fly a couple of miles to find a mate or an appropriate host crop for their eggs, will 20 or 50 or 100 feet of isolation space make any real difference? Probably not IMHO.

Your best bet is heavy use of Bt powder during the summer. I spread it around my garden on various crops about every 10 days. Alas, I admit that I do not get black swallowtail or monarch larvae in my yard, but I also don't have problems with cabbage worms or corn earworms or tomato hornworms. Unless I forget for at least a month. The beauty of Bt is that it's safe, cheap, and easy to apply. I use my "Dustin' Mizer" and do it on a windy day for maximum dispersal. Biologic warfare at its best.

Here is a link that might be useful: Corn earworm aka tomato fruitworm

Just discovered that you posted this same question on 4 different forums here so we are duplicating answers all over the place.

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Dave

I get tomato fruitworms, Helicoverpa (Heliothis) zea (zea= corn.) I've never grown corn -- I feel like it is too much of a space-hog for my garden. That doesn't stop the moths from laying their eggs in my yard, though. I also don't regularly use Bt or any other insecticide, organic or otherwise. I grow flowers that are attractive to parasitic wasps, and watch for eggs and signs of the fruitworms (and pick them when possible.) The problem is almost always self-limiting -- I lose some tomatoes, but I see signs of parasitized eggs by early August.

Space your tomatoes as far away from your corn as you want them. Don't make that spacing decision based on this pest.

Here is a link that might be useful: Tomato Fruitworm IPM info from UC Davis

A few feet.

Corn is a super heavy feeder and leaves the soil drained depleted of nutrients. I gave up corn for this reason. I rather have good soil for other veggies.

Tomatoes also feed heavy. both also drink a lot of water. I would not want the roots close together.

Once you grow corn on an area it is best to do a 4 year cycle. that means very little push on that land the next 3 years to build it back up with green manure cover crops.

Corn is not suitable for a back yard garden.

Last year my tomatoes grew into my corn and used it for support. My neighbour couldn't figure out what I was growing. It worked out well for the tomatoes. The season was too short for the corn.

I'm experimenting because I can use the corn stalk as a support for the tomato stalk and have a cucumber plant growing out of the side of the planter. I'm using the three sisters technique except with the corn and tomato. I hope it works time will tell.

brittany overton, good for you, I look forward to how well this works for you.

Intercroping is a thing, the sister is just a sample of many that work. Like tee pee running beans with lettuce, radishes & carrots inside of the teepee, to shade them from late spring sun. The teepee thing is a good children garden project & easy for child to make & harvest.